Ширина этого стола слишком большая для нашей кухни.

Because ширина means width, and in Russian words like width, length, height, size often take the thing being measured in the genitive:

• ширина стола = the width of the table
• длина дороги = the length of the road
• высота дома = the height of the house

So ширина этого стола literally means the width of this table.

Because этого has to match стола, and стола is genitive singular masculine.

Compare:

• этот стол = this table (nominative)
• ширина этого стола = the width of this table (genitive)

So этого is just the genitive form of этот.

Because it agrees with ширина, which is a feminine singular noun.

In this sentence, the grammatical subject is not стол but ширина. So the adjective must match ширина:

• ширина → feminine singular
• большая → feminine singular

That is why you get Ширина ... слишком большая.

Russian is saying The width of this table is too large for our kitchen, so большая modifies width, not table.

That is why the sentence uses:

• ширина ... слишком большая = the width is too large

If you want the more direct idea This table is too wide for our kitchen, Russian would usually say:

• Этот стол слишком широкий для нашей кухни.

Both are correct, but they are structured differently:

• Ширина этого стола слишком большая... = focuses on the measurement
• Этот стол слишком широкий... = focuses on the table itself

In the present tense, Russian usually omits the verb to be.

So English:

• The width of this table is too large

becomes Russian:

• Ширина этого стола слишком большая

There is no present-tense is in normal Russian sentences like this.

The preposition для takes the genitive case.

So:

• для кухни = for the kitchen
• для нашей кухни = for our kitchen

Here:

• кухня → кухни in the genitive
• наша → нашей to agree with кухни

So для нашей кухни is a standard для + genitive phrase.

Because нашей is the genitive singular feminine form of наша.

The noun кухня is feminine, and after для it becomes genitive:

• nominative: наша кухня
• genitive: нашей кухни

So нашей matches кухни in gender, number, and case.

It is grammatical and natural, but it sounds a little more explicit or formal than the simpler version.

Compare:

• Ширина этого стола слишком большая для нашей кухни.
  = The width of this table is too large for our kitchen.

• Этот стол слишком широкий для нашей кухни.
  = This table is too wide for our kitchen.

The first version sounds like someone is talking about dimensions or measurements. The second version is more likely in everyday speech.

Yes. Russian word order is flexible, though not random.

The sentence as written is neutral:

• Ширина этого стола слишком большая для нашей кухни.

But you could also say:

• Для нашей кухни ширина этого стола слишком большая.

This puts more emphasis on for our kitchen.

Or, more naturally in everyday speech:

• Этот стол слишком широкий для нашей кухни.

So the basic meaning stays the same, but word order can shift emphasis or style.

Yes. You may also hear:

• Ширина этого стола слишком велика для нашей кухни.

This means almost the same thing: The width of this table is too great for our kitchen.

A rough style difference:

• слишком большая = plain, straightforward
• слишком велика = a bit more formal or literary

Both are correct.

Слишком means too in the sense of more than is acceptable or suitable.

So:

• слишком большая = too big / too large

This is different from:

• очень большая = very big

So:

• очень большая = large, but maybe okay
• слишком большая = excessively large, not okay for the situation

In this sentence, it means the table’s width is more than the kitchen can reasonably accommodate.